Yes it is quite possible that the mpg is driver related...but he has driven my 74 318 2bbl auto truck quite a bit and it never used this much gas so I'm kinda leaning toward tune up on this 77...we shall see once I get some time this week to wrench on it...

1968 Plymouth GTX
1974 Dodge P/U Long Bed Stepside 318
2019 Ram 2500 6.4, auto, 4WD